The present invention relates generally to directional or horizontal drilling devices. More particularly, the present invention relates to an electrical transmission line for use with directional or horizontal drilling machines.
Directional or horizontal drilling machines are used to drill holes along a generally horizontal path beneath the ground. After a hole is drilled, the hole is back reamed and then a length of cable or the like can be passed through the hole. Such directional drilling machines eliminate the need for digging a long trench to lay a length of cable or the like.
A typical directional drilling machine includes an elongated track that can be aligned at an inclined orientation relative to the ground. A drill head is mounted on the track so as to be moveable along the length of the track. The drill head includes a drive member that is rotated about a drive axis that is generally parallel to the track. The drive member is adapted for connection to a length of pipe, or drill stem. For example, the drive member can include a threaded end having either female or male threads.
To drill a hole using the directional drilling machine, the track is oriented at an inclined angle relative to the ground, and the drill head is retracted to an upper end of the track. Next, a length of drill stem is unloaded from a magazine and is coupled to the drive member of the drill head. Once the drill stem is connected to the drill head, the drill head is driven in a downward direction along the inclined track. As the drill head is driven downward, the drive member is concurrently rotated about the drive axis. Typically, a cutting element or drilling/boring member, is mounted at the distal end of the drill stem on the drill head. Consequently, as the drill head is driven down the track, the rotating drill stem is pushed into the ground thereby causing the drill stem to drill or bore a hole. By stringing multiple drill stems together, it is possible to drill holes having relatively long lengths.
After drilling a hole, it is common for a back reamer to be connected to the end of the drill string. Once the back reamer is connected to the end of the drill string, the directional drilling apparatus is used to pull the string of drill stems back toward the drilling machine. As the string of drill stems is pulled back toward the drilling machine, the reamer enlarges the pre-drilled hole, and the drill stems are individually uncoupled from the drill string and loaded back into the magazine of the directional drilling machine.
In order to accurately guide the drill string, an operator must monitor the position of the drill head. The principal means for locating the position of the drill head for guiding it is to equip the drill head with an electronic device that emits electromagnetic energy. Typically, the electronic device is a radio transmitter or sonde mounted within the drill head. The sonde emits electromagnetic energy at radio frequencies which can be detected above the ground by an operator using an electromagnetic wave detection device, or the like, tuned to the same radio frequency emitted by the sonde. Accordingly, by providing feedback of the drill head's position, the drilling machine operator can make the required adjustments such that the hole is bored at the proper depth and in the proper direction.
Electrical power required to operate the sonde has typically been supplied via a conventional wire line, or a battery placed within the drill head. Several problems are associated with the conventional wire line in that it is cumbersome to feed the wire line through the drill stem. In order to extend the drill string, sections of drill stem are added at the drive head of the drilling machine. Therefore, a new length of wire must be spliced or connected to a previous length or wire in the drill string. This takes time and is not generally an efficient process, thus reducing the overall productivity and slowing down the drilling process.
Providing power to the sonde via a battery is problematic in that the energy delivered to the sonde is limited to the energy capacity of the battery. Therefore, the output signal strength emitted by the sonde is practically limited to the battery's energy capacity. Since electromagnetic waves are emitted from a source (the sonde) beneath the ground, they are greatly attenuated by the time they reach the detection device above ground. Accordingly, it is desirable to increase the energy or power delivered to the sonde to increase the strength of the electromagnetic waves emitted therefrom.
For the foregoing reasons, there is a need for an apparatus, system and method capable of providing electrical power to an electronic device located within a drill head of a drilling machine that greatly enhances the productivity of the drilling process. Furthermore, there is a need for providing power to the electronic device that is not limited by the energy capacity of a battery.